Hello, you might find some answers over on our thoracic outlet syndrome forum..TOS for short
Sounds like what many of us experience symptoms wise & posture wise.. we have had some weightlifters on the forum there too..

*you don't have to have a dx of TOS for the postings & information there to be of help to you*
http://neurotalk.psychcentral.com/forum24.html

be sure to check out the sticky threads there also..